1. Field of the Invention
The present invention involves the use of manifold venting strips in lead acid batteries.
2. Description of the Prior Art
Considerable improvement has been made in the venting of gases in storage batteries typified by lead acid secondary batteries over the last fifteen years. A vexatious problem prior thereto was the accumulation of gases within the battery enclosure and respective cells during charging and discharging of the battery. Earlier venting arrangements are disclosed in U.S. Pat. No. 3,265,538 issued Aug. 9, 1966 and entitled Multiple Vent Plug Assembly; U.S. Pat. No. 3,284,244 issued Nov. 11, 1966 and entitled Multiple Vent Plug Assembly and U.S. Pat. No. 3,597,280 issued Aug. 3, 1971 and entitled Multiple Vent Plug Assembly. A particularly attractive venting arrangement is described in detail in U.S. Pat. No. 3,879,227 issued Apr. 22, 1975 to Henning and entitled Battery Vent Plug. The gang type vent disclosed in the patent permits flow of the gases from the individual cells to a single diffuser which vents the gas to the atmosphere while at the same time retarding the flow of the electrolyte into the vent should the battery not be maintained on a horizontal plane.
A typical vent plug, as described in U.S. Pat. No. 3,879,227, includes passageways for allowing the flow of gas from the individual battery cells to a porous diffusing element, and then to a passageway leading to an external vent located in the battery enclosure. The vent plug thus provides a housing for the diffusing element and respective channels leading to and passageways leading from the diffusing element. The vent plug itself is removably insertable into one or more of the ports within the top of the battery enclosure, such ports permitting direct access into the individual cells of the battery. Thus, the generated gas during battery operation rises into the ports leading to the vent plug passageways, filters through the flame arrester or diffuser, and dissipates into the atmosphere.
A disadvantage, however, with this type of vent plug arrangement is that the plug, due to its exterior positioning and removability, is susceptible to damage due to mishandling or even removal of the flame arrester, affording the possibility that the diffusing and venting function of the plug could be compromised. A solution to this problem, particularly with the advent of the sealed batteries, is the relocation of the elements providing such functions into the interior of the battery. Thus, the aforementioned disadvantage has largely been obviated, for example, by securely attaching the housing containing the diffuser or flame arrester elements to the undersurface of said cover, i.e. within the battery enclosure. Additionally, passageways leading from the various cells to the flame arrester are fabricated in the internal structure of the battery itself. For example, such passageways from cells are often formed by a series of grooves along the top surface of the battery extending from the mouth of each of several cell ports to the mouth of the centrally located port. Once the proper amount of electrolyte is added to the cells through the ports, one or more strips either essentially planar or having complimentary grooves, is placed over the ports and heat sealed into place to preserve the sealed integrity of the sealed battery. The strip sealed over and enclosing the grooves thus provides the passageways extending to a central disposed port which in turn are in gaseous communication via a channel to the diffusing element. A vent to the atmosphere disposed adjacent to the diffusing element allows the gas to pass through the element and dissipate into the atmosphere.
While the aforementioned structure is admirably suited for the sealed or so-called maintenance-free batteries, it has not proven to be entirely satisfactory for battery applications where it is desired to have ready access to the interior of the battery. Continuous removal of the strip which is sealed to the battery top to provide access to the battery cells may result in deleterious effects to the strip itself. Repeated removal of such a strip is a highly uneconomical technique. Additionally, loosely securing the strip to the top, in an effort to overcome repeated removal and sealing, would result in the gases leaking through the strip-battery interfaces and not moving, as desired, through the diffusing element. It is, therefore, desired to have a battery which is suited for easy access into the interior of the cell for addition of fluid to the electrolyte and the like while preserving the venting function through an interiorly positioned flame arrester.